PRR T1
Encyclopedia
The Pennsylvania Railroad
's 52 T1 class duplex-drive
4-4-4-4
steam locomotive
s, introduced in 1942 (2 prototypes) and 1946 (50 production), were their last-built steam locomotives and their most controversial. They were ambitious, technologically sophisticated, powerful, fast, and uniquely streamlined
by Raymond Loewy
. However, they were also prone to violent wheelslip
both when starting and at speed, complicated to maintain, and expensive to run. In 1948, the PRR vowed to place diesel locomotive
s on all express passenger trains, leaving unanswered whether the T1's flaws were solvable.
However, a Spring, 2008 article in the Pennsylvania Railroad Technical and Historical Society Magazine revealed that the wheel-slip problems were caused by the failure to properly train engineers transitioning to the T1, resulting in excessive throttle applications, which in turn caused the wheel-slips on this very powerful locomotive.
of 1914, produced until 1928. Two experimental enlarged K5
locomotives were produced in 1929, but they were not considered enough of an improvement to be worthwhile. After that point, the PRR's attention switched to electrification
and the production of electric locomotive
s; displaced steam locomotives meant that the railroad had an excess of steam power and no real need for additional locomotives.
However, the deficiencies of the K4s became more and more glaringly obvious as the 1930s progressed. They were fine locomotives, but as train lengths increased, they were simply not big enough for the task. Double headed K4s locomotives became the norm on heavy trains. The railroad had the locomotives to spare, but paying two crews and running two locomotives per train was simply not the most economical choice. Meanwhile, other railroads were leaping ahead, developing larger and larger passenger power. Rival New York Central built better and better Hudsons
, while other roads developed passenger 4-8-2
"Mountain" types and then 4-8-4
"Northern" designs. The PRR's steam power began to look rather outdated indeed.
In the mid to late 1930s, the PRR began to develop steam locomotives again, but with a difference. Previous PRR locomotive policy had been unrelentingly conservative, but new, radical designs took hold. Designers from the Baldwin Locomotive Works
, the PRR's longtime development partner, persuaded the railroad to adopt Baldwin's latest revolutionary idea: the duplex locomotive
. This split the locomotive's driving wheels into two sets and gave each set its own pair of cylinders and rods. Previously, the only locomotives with split sets of drivers were articulated locomotive
s, but the duplex used one rigid frame. In a duplex design, cylinders could be smaller, pistons could be faster, and the weight of side and main rods could be drastically reduced. Given that the movement of the main rod cannot be fully counterbalanced, the duplex design would drastically reduce "hammer blow" on the track. The lower the weight of the reciprocating mass meant that higher speeds could be more easily achieved. Use of poppet valves also increased the speed each set of drivers could achieve because they gave very accurate steam delivery to the cylinders. However, there was a drawback of the metallurgy used, meaning that the poppet valve could not take the stress of sustained high speed operation (meaning over 100 mi/h. on production T1s).
The first PRR duplex was the single experimental S1
of 1939. This proved successful, but it was simply too large a locomotive, and its size prohibited it from operating over most of the PRR's network. The concept being seemingly proven, the PRR returned to Baldwin to develop a duplex design fit for series production. The two Baldwin prototypes (#6110 and #6111) delivered glowing test reports, resulting in a production order for 50 T1s, split between the PRR's own Altoona Works and Baldwin. The last production T1 (#5549) entered service on August 27, 1946.
Engine #5539 developed 5012 HP, as tested between September 11, 1946 and September 14, 1946 by C&O dynamometer car DM-1 while on loan to the C&O.
Due to their high level of complexity relative to other steam locomotive designs, T1s were known to be difficult to maintain. The T1s were also so powerful that they could easily exceed their designed load and speed limitations, which in turn often caused wear and tear issues. A technician charged with determining the cause of frequent poppet valve failures on the T1s claimed to have observed them being operated at speeds of up to 140 mph (225 km/h) between station stops in order to make up time on trains that had been delayed. The T1 was designed to run reliably at speeds of up to 100 mi/h. Although such reports are viewed as rather dubious, it is generally accepted that T1s regularly exceeded 100 mph (161 km/h) in day-to-day operation, making them among the fastest steam locomotives ever built. The price paid for such excessive speed was higher maintenance costs and increased failures in service.
The T-1 4-4-4-4 had such power that the engineer, if not careful on the throttle, could have violent wheel slip at 100 mi/h, causing damage to the poppet valves. They were described as "free steaming", meaning they could maintain boiler pressure regardless of throttle setting.
Most T1s, having been displaced by new diesels, were out of service by 1952. All T1 locomotives were sold for scrap between 1951 and late 1955. The last engines were towed westward for scrapping in early 1956. However, an exact scale live steam
replica in 1 inch/foot scale (1:12) has been built by Ed Woodings, using the original T1 plans. In addition, the T1 has proven a fairly popular subject to be reproduced in model form.
Pennsylvania Railroad
The Pennsylvania Railroad was an American Class I railroad, founded in 1846. Commonly referred to as the "Pennsy", the PRR was headquartered in Philadelphia, Pennsylvania....
's 52 T1 class duplex-drive
Duplex locomotive
A duplex locomotive is a steam locomotive that divides the driving force on its wheels by using two pairs of cylinders rigidly mounted to a single locomotive frame; it is not an articulated locomotive...
4-4-4-4
4-4-4-4
A 4-4-4-4 steam locomotive, in the Whyte notation for describing locomotive wheel arrangements, has a four-wheel leading truck, two sets of four driving wheels, and a four-wheel trailing truck.Other equivalent classifications are:...
steam locomotive
Steam locomotive
A steam locomotive is a railway locomotive that produces its power through a steam engine. These locomotives are fueled by burning some combustible material, usually coal, wood or oil, to produce steam in a boiler, which drives the steam engine...
s, introduced in 1942 (2 prototypes) and 1946 (50 production), were their last-built steam locomotives and their most controversial. They were ambitious, technologically sophisticated, powerful, fast, and uniquely streamlined
Streamliner
A streamliner is a vehicle incorporating streamlining in a shape providing reduced air resistance. The term is applied to high-speed railway trainsets of the 1930s to 1950s, and to their successor "bullet trains". Less commonly, the term is applied to fully faired recumbent bicycles...
by Raymond Loewy
Raymond Loewy
Raymond Loewy was an industrial designer, and the first to be featured on the cover of Time Magazine, on October 31, 1949. Born in France, he spent most of his professional career in the United States...
. However, they were also prone to violent wheelslip
Locomotive wheelslip
Locomotive wheelslip is an event that affects railway motive power when starting from stationary.The greatest effort is required from a locomotive when starting...
both when starting and at speed, complicated to maintain, and expensive to run. In 1948, the PRR vowed to place diesel locomotive
Diesel locomotive
A diesel locomotive is a type of railroad locomotive in which the prime mover is a diesel engine, a reciprocating engine operating on the Diesel cycle as invented by Dr. Rudolf Diesel...
s on all express passenger trains, leaving unanswered whether the T1's flaws were solvable.
However, a Spring, 2008 article in the Pennsylvania Railroad Technical and Historical Society Magazine revealed that the wheel-slip problems were caused by the failure to properly train engineers transitioning to the T1, resulting in excessive throttle applications, which in turn caused the wheel-slips on this very powerful locomotive.
Development
The last production express passenger class the PRR had produced was the K4sPRR K4s
The Pennsylvania Railroad's K4s 4-6-2 "Pacific" was their premier passenger-hauling steam locomotive from 1914 through the end of steam on the PRR in 1957....
of 1914, produced until 1928. Two experimental enlarged K5
PRR K5
The Pennsylvania Railroad's class K5 was an experimental 4-6-2 "Pacific" type, built in 1929 to see if a larger Pacific than the standard K4s was worthwhile. Two prototypes were built, #5698 at the PRR's own Altoona Works, and #5699 by the Baldwin Locomotive Works. Although classified identically,...
locomotives were produced in 1929, but they were not considered enough of an improvement to be worthwhile. After that point, the PRR's attention switched to electrification
Electrification
Electrification originally referred to the build out of the electrical generating and distribution systems which occurred in the United States, England and other countries from the mid 1880's until around 1940 and is in progress in developing countries. This also included the change over from line...
and the production of electric locomotive
Electric locomotive
An electric locomotive is a locomotive powered by electricity from overhead lines, a third rail or an on-board energy storage device...
s; displaced steam locomotives meant that the railroad had an excess of steam power and no real need for additional locomotives.
However, the deficiencies of the K4s became more and more glaringly obvious as the 1930s progressed. They were fine locomotives, but as train lengths increased, they were simply not big enough for the task. Double headed K4s locomotives became the norm on heavy trains. The railroad had the locomotives to spare, but paying two crews and running two locomotives per train was simply not the most economical choice. Meanwhile, other railroads were leaping ahead, developing larger and larger passenger power. Rival New York Central built better and better Hudsons
NYC Hudson
Hudson was the name given to the 4-6-4 steam locomotive wheel arrangement by the New York Central Railroad which was the first to use locomotives of this type in North America.-History:...
, while other roads developed passenger 4-8-2
4-8-2
Under the Whyte notation for the classification of steam locomotives, 4-8-2 represents the wheel arrangement of four leading wheels on two axles , eight powered and coupled driving wheels on four axles, and two trailing wheels on one axle...
"Mountain" types and then 4-8-4
4-8-4
Under the Whyte notation classification of steam locomotives, 4-8-4 represents the wheel arrangement of four leading wheels on two axles , eight powered and coupled driving wheels on four axles, and four trailing wheels on two axles .Other equivalent classifications are:UIC classification: 2D2...
"Northern" designs. The PRR's steam power began to look rather outdated indeed.
In the mid to late 1930s, the PRR began to develop steam locomotives again, but with a difference. Previous PRR locomotive policy had been unrelentingly conservative, but new, radical designs took hold. Designers from the Baldwin Locomotive Works
Baldwin Locomotive Works
The Baldwin Locomotive Works was an American builder of railroad locomotives. It was located in Philadelphia, Pennsylvania, originally, and later in nearby Eddystone, Pennsylvania. Although the company was very successful as a producer of steam locomotives, its transition to the production of...
, the PRR's longtime development partner, persuaded the railroad to adopt Baldwin's latest revolutionary idea: the duplex locomotive
Duplex locomotive
A duplex locomotive is a steam locomotive that divides the driving force on its wheels by using two pairs of cylinders rigidly mounted to a single locomotive frame; it is not an articulated locomotive...
. This split the locomotive's driving wheels into two sets and gave each set its own pair of cylinders and rods. Previously, the only locomotives with split sets of drivers were articulated locomotive
Articulated locomotive
Articulated locomotive usually means a steam locomotive with one or more engine units which can move independent of the main frame. This is done to allow a longer locomotive to negotiate tighter curves...
s, but the duplex used one rigid frame. In a duplex design, cylinders could be smaller, pistons could be faster, and the weight of side and main rods could be drastically reduced. Given that the movement of the main rod cannot be fully counterbalanced, the duplex design would drastically reduce "hammer blow" on the track. The lower the weight of the reciprocating mass meant that higher speeds could be more easily achieved. Use of poppet valves also increased the speed each set of drivers could achieve because they gave very accurate steam delivery to the cylinders. However, there was a drawback of the metallurgy used, meaning that the poppet valve could not take the stress of sustained high speed operation (meaning over 100 mi/h. on production T1s).
The first PRR duplex was the single experimental S1
PRR S1
The PRR S1 class steam locomotive was an experimental locomotive that was the largest rigid frame passenger locomotive ever built. The streamlined Art Deco styled shell of the locomotive was designed by Raymond Loewy....
of 1939. This proved successful, but it was simply too large a locomotive, and its size prohibited it from operating over most of the PRR's network. The concept being seemingly proven, the PRR returned to Baldwin to develop a duplex design fit for series production. The two Baldwin prototypes (#6110 and #6111) delivered glowing test reports, resulting in a production order for 50 T1s, split between the PRR's own Altoona Works and Baldwin. The last production T1 (#5549) entered service on August 27, 1946.
Engine #5539 developed 5012 HP, as tested between September 11, 1946 and September 14, 1946 by C&O dynamometer car DM-1 while on loan to the C&O.
Due to their high level of complexity relative to other steam locomotive designs, T1s were known to be difficult to maintain. The T1s were also so powerful that they could easily exceed their designed load and speed limitations, which in turn often caused wear and tear issues. A technician charged with determining the cause of frequent poppet valve failures on the T1s claimed to have observed them being operated at speeds of up to 140 mph (225 km/h) between station stops in order to make up time on trains that had been delayed. The T1 was designed to run reliably at speeds of up to 100 mi/h. Although such reports are viewed as rather dubious, it is generally accepted that T1s regularly exceeded 100 mph (161 km/h) in day-to-day operation, making them among the fastest steam locomotives ever built. The price paid for such excessive speed was higher maintenance costs and increased failures in service.
The T-1 4-4-4-4 had such power that the engineer, if not careful on the throttle, could have violent wheel slip at 100 mi/h, causing damage to the poppet valves. They were described as "free steaming", meaning they could maintain boiler pressure regardless of throttle setting.
Today
Live steam
Live steam is steam under pressure, obtained by heating water in a boiler. The steam is used to operate stationary or moving equipment.A live steam machine or device is one powered by steam, but the term is usually reserved for those that are replicas, scale models, toys, or otherwise used for...
replica in 1 inch/foot scale (1:12) has been built by Ed Woodings, using the original T1 plans. In addition, the T1 has proven a fairly popular subject to be reproduced in model form.
External links
- Chesapeake & Ohio Tests the PRR T1 - Chesapeake and Ohio Historical Magazine, May 2005 by Stephenson, David R - The C&O test report contains information that is not widely known, and some of it contradicts generally accepted beliefs about the T1.
- Photos of PRR 4-4-4-4 locomotives
- An N Scale PRR T1 4-4-4-4 scratchbuilding project